FIG. 1 is a flow chart depicting a conventional method 10 for fabricating a conventional magnetoresistive (MR) sensor. For simplicity, some steps are omitted. The conventional method 10 is used for providing a giant magnetoresistive (GMR) sensor, such as a spin valve or spin tunneling junction. The MR stack is provided, via step 12. Step 12 typically includes blanket depositing the layers of the MR sensor. For example, seed layers, an antiferromagnetic (AFM) layer, a pinned layer such as a synthetic antiferromagnetic (SAF) layer, a nonmagnetic spacer layer, a ferromagnetic or SAF free layer, and capping layer(s) may be blanket deposited in step 12. The conventional MR sensor is defined at least in the track width direction, via step 14. Typically, this is accomplished by covering a portion of the MR stack and milling away an exposed portion of the conventional MR stack using a conventional ion mill.
Hard bias structures are provided, via step 16. Step 16 is typically performed by blanket depositing the hard bias material, then removing the mask on the conventional MR sensor. The hard bias structures are typically high coercivity materials. Thus, once their magnetization is set in a particular direction, magnetization of the hard bias layers should remain stable. The magnetization of the hard bias is set in the direction desired for biasing the free layer, via step 18. Step 18 thus includes subjecting the transducer being fabricated to a large field along the easy axis of the free layer. For example, fields of approximately one Tesla may be applied in a desired direction along the easy axis of the free layer.
After the hard bias structures have been provided, the transducer is still subject to subsequent processing. Thus, for example, a photoresist layer is provided, via step 20. Step 20 may include spinning coating or otherwise depositing the photoresist layer. The photoresist is then cured, via step 22. Consequently, the transducer is subject to an elevated temperature, often for long times. For example, in some cases, the photoresist cure is at temperatures on the order of two hundred degrees centigrade for times on the order of seven to eight hours.
Fabrication of the conventional transducer may then be completed, via step 24. Step 24 may include exposing the photoresist layer to form a mask, and other processing. For example, shield(s), a write transducer, and/or other structures may be formed. In addition, other high temperature processes may be performed.
FIG. 2 depicts a portion of a conventional read transducer 50 fabricated using the conventional method 10. FIG. 2 depicts the conventional read transducer 50 from the air-bearing surface (ABS). Thus, a read sensor 52 including AFM layer 54, SAF layer 56, nonmagnetic spacer layer 58, free layer 60, and capping layer 62. In addition, hard bias structures 64 are shown. The hard bias structures 64 have had their magnetizations 65 set in step 18. In this state, the conventional transducer may go through the photoresist cure in step 22 and other high temperature steps.
Although the conventional method 10 may provide the conventional read transducer 50, there are drawbacks. In particular, the MR sensor 52 may have an undesirable amount of noise. In particular, the signal-to-noise ratio (SNR) of the MR sensor 52 may be degraded.
Accordingly, what is needed is an improved method for fabricating a MR sensor 52 having hard bias structures 64 with acceptable SNR.